Cryptographic device



March 5, 1946. w. F. FRIEDMAN CRYPTOGRAPHIC DEVICE Filed Oct. 1-9, 19393 Sheets-Sheet 1 lll March 5,l 1946.

w. F. FRIEDMAN 2,395,863

CRYPTOGRAPHIC 'DEVICE Filed Oct. 19, 1939 3 Sheets-Sheet 2 March 5,1946. w. F. FRIEDMAN 2,395,863

CRYPTGRAPHIC DEVI CE Filed Oct. 19, 1939 3 Sheets-Sheet 3 Patented 5,1946 UNITED STATE s PATENT ori-'ICE oRYP'roGRAPIIIc DEVICE William F.Friedman, washington, D. c.

' Application October 19, 1939, Serial No. 300,212

(Cl. :l- 2) (Granted under the act of March 3, 1883,- as

amended April 30, 1928; 3'10 0. G. 757) l 19 Claims.

requiring the use of sliding alphabets.

The invention is described with reference the accompanying drawings, inwhich:

Fig. 1 is a perspective showing one form 0r embodiment of the invention;

Fig. 2 is a top plan view of another embodiment of the invention: I

Fig. 3 is a cross-section taken on the line 3 3 of Fig. 2;

Fig. 3a is a fragment of the same section on an enlarged scale showingthe T-grip for the guide Arule in operative position;

Fig. 4 is a top View of the form of invention of i Fig. 1 showing theguide rule in shifted position;

Fig. 5 is a top plan View showing another embodiment of the invention inwhich the base is composed of separate detachable grooved sections;

Fig. 6 is a perspective .grooved sections; and l h Fig. 7 is aperspective showing a frame structure Aand sub-base on which saidgrooved sections may be assembled.

Y Referring to Fig. 1, in this embodiment the device comprises abase I,on which are horizontally fastened a series of cylindrical rods 2,forming a set of channel ways 3, into which character bearing strips 4,may be/ inserted and slid from left` to rightor vice versa". In thespecic embodiment `disclosed herein the device comprises twenty-fivesuch channel ways, but the device is byno means limited to this number.The number chosen in thistembodiment is merely a convenient number, andit may be increased or decreased within certain limits in otherembodiments Without materially departing from the spirit of theinvention. A rule, or reading guide 5, attached to a reading guidevslide6, can be slid to the left or right on a reading guide slide rail 1. Endbars 8 and 9, serve as stops against which' the reading guide `5 may bebrought at the end of its travel to the left or right. To the back ofthe base I is fas- 1 tened a hinged support I0, which can be pulled outto support the devicein a slanting position as showing one of th'e itrests upon a table, desk, or other plane surface. Or, if th'e operatorprefers to lay the device at upon the table, the rubber feet Il, at thefour corners of the bottom of base I Will'support the device and keep itfrom sliding about on the table.

. cryptographic and cryptanalytic investigations As stated above, intothe channel ways 3 there are inserted character strips 4 of paper orother suitable material, hereinafter called alphabet strips, upon whichappear sequences of 1ette.s of the alphabet,each sequence being repeatedon the strip, and the letters being equidistant from one anotherthroughout. The purpose of the duplication of sequence will appearpresently. The letters on the alphabet strips may be in normal order orin disarranged order; if the latter,

the various alphabets may or may not be different. Assuming, however,different alphabets are being used, each strip bears an identifying marksuch as a number I4, so that the alphabet i strips may be inserted intothe channel ways 3 according to some preagreed key. For example, in Fig.1 is shown a set of twenty-five channel ways into which Ytwenty-fivediierent alphabet strips 4 have been inserted according to the followingkey, reading from the top downward:

for use either to encipher aplainglanguagemessage or to decipher acryptogram `Whichzhas fbeen enciphered by means of the` device,alphabetsgfand key shown in Fig. l.v ySuppose this plainstext' messageis to be enciphered: t f.. 1

FROM MILI'I'ARY AUTHQRITIES Moving the reading guide 5 to the left, andbringing it against the left end bar 8, the operator proceeds to align,in a column immediately to the right of the reading guide, the firsttwentyfive letters of the message. This is most conveniently done byplacing the eraser end of a pencil upon the successive desired lettersas found on the successive alphabet strips 4 from the vtop downwards,and pulling or pushing the alphabet strips in their channel Ways towardthe reading guide so that each strip stops with the proper letter justto the right of the right-hand edge of 2 the reading guide s. when thealphabet strips `are being aligned on the left-hand side of the device,as in the above procedure, the operator connes his search' for lettersto the left-hand half of the duplicated sequence on each alphabet strip.

When all twenty-five alphabet strips have been aligned as indicated,there is disclosed a multiplicity of columns of lettersjto the right ofthe plain-text column of letters thus aligned. All these columns ofletters, except one, are columns of cipher letters, each columnrepresenting a cipher equivalent of the plain-text column. The singleexception is the column which is the twenty-fifth removed from theplain-text column set up by the operator, and is merely a repetition ofthatplain-text column. One of these cipher columns is selected at randomand is recorded in five-letter groups. The reading guide is useful inthis operation, since by placing it alongside the column selected,reading of the cipher column is facilitated. Suppose that the readingguide 5 be moved so that its left-hand edge aligns a column of ciphertext. As shown in Fig. 4, such a column would read as follows:

SNAFJ `L IXRJCi GVWVA ATVWW PVNUT These letters are recorded andconstitute the cipher letters for the twenty-ve plain-text letplain textare aligned against the left edge of the reading guide S. Again a set of`columns of cipher letters are disclosed to the left of the readingguide. One of these columns is selected at random and again a set oftwenty-five cipher letters representing the second set of twentylveplain-text letters is recorded. If the message contains more than fiftyletters, the foregoing procedure is repeated until the entire mess agehas been enciphered There is no need to indicate tothe recipient of themessage which column is selected for the cipher equivalent of each setof twenty-five plain-text letters, as will be noted presently.

Io decipher the message, having the alphabets and the key according towhich they have been arranged, the operator merely proceeds as inencipherment, aligning the alphabet strips in their channel ways so thatthe first twenty-five cipher letters of the cryptogram are in onecolumn. He then examines all the other twenty- `five columns of letters,looking for one which "contains intelligible text throughout its extentf from top to bottom.

There will be one and only one such column, and. this will be theplaintext equivalent of the column of cipher text set up on the device.The reading guide 5 is useful in this Search for the plain-text column,rs it can readly be moved to scan the successive colk umns vfrom left toright, or from right to left.

The plain-text column thus found is recorded yin word lengths andtheoperator proceeds to set up the next twenty-live cipher letters onthe right-hand side of the device. Again he looks for -a plain-textcolumn and records it when found. He lcontinues this process until themessage has been completely deciphered.

In the form of invention shown in Fig. 2,-v the device comprises' a pairof hinged components F`F' of metal, Bakelite or other suitable materialand foldable on one another in the manner of a book. As here shown, thegrooved slideways 3 are formed on the inner faces of the said componentsby milling, or in the case where a condensation product such as Bakeliteis used, may be molded in the material. In the embodiment disclosed,there are a total of thirty such slideways, fifteen in each component,though it will be understood that the invention is not limited to anyvparticular number. It will be noted that the slideways are open at theiropposite ends yso that the alphabet strips may be readily inserted andfreely extended outwardly therefrom as they are slid into differentpositions in the operations of enciphering and deciphering. As in otherforms of the invention, a T-grip 6 is attached to the guide rule 5 atits end for the purpose of manipulating the rule, and is slidable in achannel 20 having therein undercut grooves 2l and 22 formed laterallyalong its inside edges. The grip 6 is provided with a spring-pressedelement 23 engaging in bottom groove 2l, and having an oppositelydisposed bead 24 engaging in the opposite groove 22 whereby the grip 6is maintained under suitable sliding tension in the channel 20, andwhereby the guide rule 5 is manipulated transversely in relation to thealphabet strips d; and the opposite end of the rule is adapted to slidefreely in a lateral undercut groove 25 formed in component F'. The grip6 is rigidly secured to the guide rule 5 in the manner of a T-square andmay be so manipulated that the rule affords a positive means ofobtaining an accurate alignment in column formation of the characters onsaid alphabet strips and in varying relations for cryptographic purposesThis foldable form of device presents a number oi practical advantages,among which may be mentioned its compactness and portability; also thefoldable feature permits exclusion of dust and dirt.`

While in one form of device here disclosed, cylindrical rods are securedto a base at regular intervals from one another to form the channel waysinto which the alphabet strips are inserted, it should be understoodthat any other means may be employed to form the channel ways.

For example, a series of elongated metal strips known in the trade ascard holders, used names of mail-box owners in apartment houses, etc.,may =be used to form the channel ways; these card holders may be rivetedto the base, or spot welded to it, or attached in any other suitablemanner. Or as disclosed in connection with Fig. 2, the channel ways maybe formed by milling grooves in the base l itself, which may be made ofmolded Bakelite, for example. In such case the grooves are made by arotating cutterV which undercuts at the two edges, forming a channel waysuch as is commonly found in slide-rules. Figure 6 shows such a sectionin the form of a piece of Bakelite or similar material I3, in which fivesuch channel ways 3 sections can be made according to subsidiary keys.

Referring to Fig. 7, the sub-base la is a plane i fageea'sce surfacewhich is provided with an undercut. alot- I4, for carrying a slidingclamp I5,v provided with I a knurled thumb screw IB, for fastening theclamp into position. End bars` 8 and 8' elevated above the base bysupports l] and back stop I8, serve the same purpose as similarly7 ofFig. 1.

Using a sub-base suchas that designated end bars lshown in Fig.I 7,

bearing thereon alphabetic character sequences and individually movablein said ways; and means adjustable transversely of said strips tofacilitate the reading of said characters in varying relations forenciphering and deciphering messages.

5. A cryptographic device comprising a base having vertically groovedslide-ways formed therein; strips bearing thereon alphabetic charwlthseveral sections such as that shown in Fig. 6, t

one method of operation of this embodiment of i the invention is shownin Fig. 5. I n that figure there are iive sections of 3, 4', 5, 7 and 8channel ways, giving a total of twenty-seven channel ways. First, thesections are temporarily fastened to the base in the alphabetical orderof their identifyingl symbols. Then the'twenty-seven alphabet stripswould be inserted in the twenty-seven lconsecutive channel waysaccording to the predetermined numerical key already referred to abovein connection with Fig. l. To encipher a given message, there would thenbe a subsidiary or speciiic key, also arranged for in advance by meansof an indicator in the message, which would direct that the sections benow placed onto the base in a mixed order, say E-D--A-B-C, as shown' in-Fig. 5. `The encipherment of a message would then proceed exactly asbefore. In anotherv message, the indicator for the sectional arrangementmight be diiierent, say onecalling for the seve sections there could be120 different arrangements of sections on the base, even though only oneset of alphabet strips is employed. The purpose of this is, of course,to increase the keying i, possibilities of the device, and to impartuniqueV acter sequences and individually slidable in said ways; andmeans adjustable transversely of said strips for facilitating thereading of said characters in varying relations for enciphering 'anddeciphering messages.

6. A cryptographic device comprising a base provided with a plurality ofchannel ways; alpha-` betbearing strips adapted to be individuallyinserted and aligned .in varying ,relations in said ways forcryptographic purposes; and a slidable y channel ways;

guide rule for making excursions transversely along the channel ways andin relation to said strips for enciphering and deciphering messages.

7. A cryptographic device comprising a base V having a supporting foothingedly attached to the under surface of said base; a plurality ofmembers iixed to the obverse surface of the base at equidistantintervals to form a. plurality 4of strips bearing alphabetic se-`quences of characters individually slidable in said ways;` a guide ruleadapted to be moved trans- `versely of said strips to facilitate thereading of selected sequences of characters in varying relations forcryptographic purposes; and stop members for the guide rule disposed atopposite ends u of said channel'ways. y

nothing` further need be said on this score except that there hasexisted for many years a hitherto unfulfilled need for a simple deviceof this type, suitable for the insertion of sliding alphabets.

Changes, modifications and equivalent arrangements are contemplatedwithin the scope of the invention as defined by the appended claims.

I claim:Y

l. A cryptographic provided' with a plurality of horizontal channelways; strips provided with discrete sequences of equally spacedalphabetic characters adapted for insertion therein and adjustableindependently ofl one another and means for facilitating the reading ofsaid characters in selected columns. 4

2. A cryptographicdevice comprising a base, said base being providedAwith a plurality of vertical channel. ways, and individually adjustablestrips bearing discrete sequences of equally spaced alphabeticcharacters adapted to be slidably inserted therein; and means forfacilitating the reading of said characters in selected columns and indifferent relations for cryptographic purposes.

3. A cryptographic device comprising a rbase formed with horizontallygrooved slide-ways therein; individually adjustable alphabeticstripsslidable in said ways; and means to facilitate the reading of selectedalphabetic columns in Varying relations for `cryptographic purposes.

4. A cryptographic device comprising a base device comprising a base 8.A cryptographic device comprising a subbase; interchangeablebase-sections having grooves formed therein to provide a, plurality ofchannel ways; means for removably attaching said sections in position onsaid sub-base to perl mit different arrangements of said sections injuxtaposed relationship -for cryptographicfpurposes;` character bearingstrips adapted for slidable insertion in said channel ways; `and aslidable guide rule movable transversely across said channel ways and invarying relations to said strips for enciphering and decipheringmessages.

9. A combination according to claim `8 in`which said grooved sectionsare of the same size and contain equal numbers of channel ways.'

10. A combination according to claim 8, in

which saidl grooved sections are of different sizes an'd contain unequalnumbers of channel ways.

11. A combination according to claim 8 in which stops are provided atthe opposite ends of the channel ways to limit the movement of the sliderule at the end of its travel.

12. A cryptographic device comprising a frame structureand including asub-base formed there- `in varying relations with respect to said char-Aacters for enciphering and deciphering messages.

13. A cryptographic device comprising a frame structure and including asub-base therein; base-sections grooved to provide a plurality ofchannel Ways, said sections having different numbers of said channelways and being differentiated from one another by distinguishingsymformed with grooved slide-ways therein; strips bols: meansfordetachably securing said sections on the sub-base to permit diilerentjuxtaposed arrangements thereof for cryptographic purposes; stripsbearing alphabetic sequences oi characters movable in said channel ways;a. guide rule slidable transversely of said strips and alignable invarying relations with said characters for enciphering and decipheringmessages; and stop members at opposite ends of the' channel ways tolimit the movement of the slide rule at the end of its travel. v

14. A cryptographic device comprising a multiple base formed of separatesections, said sections being interchangeable with 'one another topermit different juxtaposed arrangements for cryptographic purposes; a.pluralityof channel aciers in varying relations for enciphering andvdeciphei-ing messages.

17. A cryptographic device composed of hinged sections foldable upon oneanother, said sectionsA aciers; `and a guide rule hinged to told withsaid ways in said sections; strips bearing sequences of characters andindividually sldable in said ways; and a guide rule movable transverselyof said strips and alignable with said characters in varying relationsfor enciphering and deciphering messages.

15. A cryptographic device including a multi-y iorm base composed ofseparate sections, said sections having grooved slide-ways therein andbeing interchangeable with one another to permit diierent juxtaposedarrangements for cryptographic purposes; strips slidable in said waysand bearing thereon sequences of alphabetic characters; and guide meansdisposed transversely of said strips and movable to facilitate alignmentof the characters in varying relations for enciphering and decipheringmessages.

16. A cryptographic device composed of hinged sections foldable upon oneanother, said sections having grooved slide-ways formed on their innerfaces; strips slidable in said ways and bearing thereon sequences ofalphabetic characters: and guide means disposed transversely of saidstrips and movable to facilitate alignment of the charsections, saidrule being disposed transversely oi saidstrips and movable to facilitatereading of the characters in varying relations for enciphering anddeciphering messages.

1 18. A cryptographic device comprising a' pair oi hinged componentsfoldable Iupon one another, said components being provided on theirinner faces with open-ended"'slide ways; a guide rule hinged to foldwith said components; means operativel with one of said components tomaintain said rule in a, position transverselyof said strips and movableto `facilitate reading of the charactersin column formation and'invarying relations for enciphering and deciphering messages; and terminalstops to limit the movements of said rule at either end of its travel.

19. A cryptographic device comprising hinged components foldable uponone another, said componentsmeing provided on their inner faces with aplurality of slide Ways; a guide rule hinged to fold with saidcomponents; a grooved channel formed `along the edge oi' one of saidcomponents in parallelism with the slide ways; means including a,spring-tensioned element slidable in said channel for operating the saidrule whilefmaintaining the same in a position transversely of saidstrips,' said rule being movable to facilitate reading of the charactersin varying relations and in column formation for enciphering anddeciphering messages..

WILIIAM F. FRIEDMAN.

